Cory deaths within 2 days

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smcallis

Aquarium Advice Newbie
Joined
Aug 16, 2010
Messages
5
Location
Redmond WA
I have had Cory's in the past for as long as 10 years. I upgraded to a 20 gal long tank 8 months ago. I planted it with java fern, sword plants, anubias (blooming now).Java fern on driftwood I boiled then soaked. My paleatus went on a breeding frenzy and lasted 3 months. They laid eggs on the tank but no survivors. Any other species of Cory dies within 2-3 days of being in the tank. This is new and has been going on for a month. At first I thought it was the stock so switched species. Could this be lack of oxygen at the bottom even with a Koralia Nano powerhead (may take out as it may be too much current for C.pygmaeus). Should I add a bubble wand?
1~What type of fish is afflicted? Corydora's only. They eat well the first day then start swimming to the top and sinking down to the gravel by the second. They then swim on their side and struggle to go to the surface before dying.
2~What are your tank parameters (ammonia, nitrites, nitrates, temp, pH)? Ammonia 0, Nitrites 0, Nitrates 0, pH 7.4 using a 2 month old API Freshwater master test kit. Eerily too good? I'm a former microbiologist so I am very careful with testing.

3~ How large is the tank? 20 gal long How long has the tank been set up? 8 months

4~What type of filtration are you using? 2 AquaClear BOT power filters for 5-20 gallons, 100 gph

5~How many fish are in the tank? 5 Gold Pristella (all less than 1 inch), 3 Rummynose Tetra (small), 8 Cory pygmaeus (less than 1 inch) , 3 Cory sterbai (new to tank)

6~When is the last time you did a water change and vacuum the gravel? 24 hours ago How often do you do this? Water change every week, gravel vacuum every 2 weeks. How much water do you remove at a time? 25-30%

7~How long have you had the fish? Pristella and rummynose about 2 months, C. pygmaeus 1 month. C. sterbai 2 days.
If the fish is new, how did you acclimate it/them? Floated the bag with the fish for 15-20 min in the tank, opened the bag, folded down the top of the bag for the air pocket, added 6 oz tank water, waited 10 min, repeated 2-3 times, removed some water from the bag and repeated 2 times, removed most of the water from bag, poured water and fish into a dedicated container, then netted the fish and put them in the tank.
8~Have you added anything new to the tank--decor, new dechlorinator, new substrate, etc.? No
9~What kind of food have you been feeding your fish, have you changed their diet recently? Hikari Tropical Micropellets, Freeze dried Bloodworms, Tetra Tropical granules, Tetra min tablets, Omega One Shrimp pellets (Not ALL at the same time)

I am at a loss. The local LFS has checked my water, checked the dead fish, and then declared that I should probably consider other fish than Cory. I kept Cory's in a 10 gal with painted gravel, a couple sword plants and Anachris, with a Petsmart brand filter, and an occasional monthly water change. I even moved that tank across country in the back of a van plugged in to an outlet in the car and they lived two more years (total of 8-10 years for the lot). Temp was kept about 70F. I'm really at a loss for what to do next. No signs of bloating or white spots, fuzzy stuff. Just a death spiral dance and it's over.
I would appreciate any help with this situation. Thank you

smcallis
 
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Welcome to AA!

Cories can actually breathe at the surface. They can live in some very stagnant water, so I don't think the lack of oxygen is your problem. They're usually pretty hardy fish.

How many cories have died? If it's only been a few, I would suspect the stock quality if there's no chance that your tank has been contaminated with something that you're not testing for.

You could try the drip method of acclimation. I've had fewer casualties since I started using it.

Thanks for the wealth of information. It goes a long way towards helping us answer your questions quickly and accurately.
 
I had 2 sterbai, 3 paleatus (happily breeding for months), 3 Julii, and just today 1 pygmaeus die. This has been going on for about a month. One store recommended I switch to Prime from AquaSafe (Tetra) for my water as it could be heavy metals in my water. I have no way of testing for that. All of them die the same way-race to the top, gulp once, then float down as if they are stoned. Once at the bottom, they swim around then repeat it until they don't get up again. Two LFS's have tested my water. The last one where I got the sterbai said it could be too long acclimating. They recommended I put them in within 15 min of getting them home as our water was very compatible to the store water. It goes against all that I have read but I tried it and will see if they make it more than 48 hours.

Thanks for the reply. If you have any other suggestions, let me know. Could I have some odd bacterial bloom and need to treat the tank? I would hate to tear the tank down. Another tank I have (10 gallon) is set up the same way and no one dies there. It has 2 albino cory's and <gasp> breeding guppies. Good thing the momma is a hungry girl.
 
Welcome to AA! The recommendation to switch from Prime is BS. What temp have they been kept at? The species you list need decidedly different conditions to thrive. What changed from the time period that the paleatus were breeding? Were all the fish from the same source?
 
The temp is 76-78 F. Nothing has changed since I set up the tank. I usually keep cardinal tetras, rummynose tetra and cory. I had a school of cardinal for 5 months and the rummy nose for 8 months. Some died and were replaced or not. I have 3 rummynose that have been in the tank for 3 months (since May) and just added some others. No salt is added for the cory or plants sakes. My pH is consistently 7.2-7.4. I don't get it.
I would appreciate any suggestions. So far the sterbai I added yesterday are still alive and looking swimmingly well.
 
I agree with HN1 about switching dechlorinators. I've used both and they both work. I think the LFS was just grasping at straws.
 
FME, Sterbais do best in temps at 80+. That's a big reason that they are popular tank mates for Discus. Other than that, pH is slightly low to breed them, but should be fine otherwise. Maybe just bad stock. Ask the LFS if they have any other complaints and who their supplier is. I doubt they'll tell you, but it never hurts to ask. A lot of fish come in a bit ragged and stressed from the wholesalers. If you chose the fish soon after the shipments came in, the added move may be all that's needed to send them on a downward spiral.
 
I did add a very small fine mist bubbler to the tank. The pygmaeus swim through it. The sterbai are acting very normal. So far so good. Thanks for the help.
 
Well, one of the sterbai died overnight. All three were fine yesterday. I'm beginning to think it's the stock from the supplier. One LFS told me that one supplier stocks most of the LFS's in the area. Otherwise, my pymaeus and 2 sterbai are so far fine.
 
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